debugfs: fix wait/cancellation handling during remove

Ben Greear further reports deadlocks during concurrent debugfs
remove while files are being accessed, even though the code in
question now uses debugfs cancellations. Turns out that despite
all the review on the locking, we missed completely that the
logic is wrong: if the refcount hits zero we can finish (and
need not wait for the completion), but if it doesn't we have
to trigger all the cancellations. As written, we can _never_
get into the loop triggering the cancellations. Fix this, and
explain it better while at it.

Cc: stable@vger.kernel.org
Fixes: 8c88a474357e ("debugfs: add API to allow debugfs operations cancellation")
Reported-by: Ben Greear <greearb@candelatech.com>
Closes: https://lore.kernel.org/r/1c9fa9e5-09f1-0522-fdbc-dbcef4d255ca@candelatech.com
Tested-by: Madhan Sai <madhan.singaraju@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20240229153635.6bfab7eb34d3.I6c7aeff8c9d6628a8bc1ddcf332205a49d801f17@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert "debugfs: annotate debugfs handlers vs. removal with lockdep"

This reverts commit f4acfcd4deb1 ("debugfs: annotate debugfs handlers
vs. removal with lockdep"), it appears to have false positives and
really shouldn't have been in the -rc series with the fixes anyway.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20231202114936.fd55431ab160.I911aa53abeeca138126f690d383a89b13eb05667@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add API to allow debugfs operations cancellation

In some cases there might be longer-running hardware accesses
in debugfs files, or attempts to acquire locks, and we want
to still be able to quickly remove the files.

Introduce a cancellations API to use inside the debugfs handler
functions to be able to cancel such operations on a per-file
basis.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

debugfs: annotate debugfs handlers vs. removal with lockdep

When you take a lock in a debugfs handler but also try
to remove the debugfs file under that lock, things can
deadlock since the removal has to wait for all users
to finish.

Add lockdep annotations in debugfs_file_get()/_put()
to catch such issues.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

debugfs: fix automount d_fsdata usage

debugfs_create_automount() stores a function pointer in d_fsdata,
but since commit 7c8d469877b1 ("debugfs: add support for more
elaborate ->d_fsdata") debugfs_release_dentry() will free it, now
conditionally on DEBUGFS_FSDATA_IS_REAL_FOPS_BIT, but that's not
set for the function pointer in automount. As a result, removing
an automount dentry would attempt to free the function pointer.
Luckily, the only user of this (tracing) never removes it.

Nevertheless, it's safer if we just handle the fsdata in one way,
namely either DEBUGFS_FSDATA_IS_REAL_FOPS_BIT or allocated. Thus,
change the automount to allocate it, and use the real_fops in the
data to indicate whether or not automount is filled, rather than
adding a type tag. At least for now this isn't actually needed,
but the next changes will require it.

Also check in debugfs_file_get() that it gets only called
on regular files, just to make things clearer.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

debugfs: convert to new timestamp accessors

Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20231004185347.80880-26-jlayton@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

debugfs: convert to ctime accessor functions

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230705190309.579783-32-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

debugfs: drop inline constant formatting for ERR_PTR(-ERROR)

Stephen Rothwell reported htmldocs warning when merging driver-core tree
for linux-next:

Documentation/filesystems/api-summary:146: fs/debugfs/inode.c:804: WARNING: Inline literal start-string without end-string.

The warning is due to inline constant formatting (``%CONST``) doesn't play
nice with complex-name constants like ERR_PTR(-ERROR).

Drop the formatting for that constant above to be consistent with similar
error constants and also to fix the above warning.

Link: https://lore.kernel.org/lkml/20230220163133.481e43d8@canb.auug.org.au/
Fixes: d3002468cb5d5d ("debugfs: update comment of debugfs_rename()")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20230220124721.11657-1-bagasdotme@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: update comment of debugfs_rename()

Since commit ff9fb72bc077 ("debugfs: return error values, not NULL")
changed return value of debugfs_rename() in error cases from %NULL to
%ERR_PTR(-ERROR), the comment of debugfs_rename should also be updated
so as not to mislead readers.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Link: https://lore.kernel.org/r/20230208035634.58095-1-zhengqi.arch@bytedance.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs: port ->rename() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

fs: port ->setattr() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

debugfs: Only clobber mode/uid/gid on remount if asked

Users may have explicitly configured their debugfs permissions; we
shouldn't overwrite those just because a second mount appeared.

Only clobber if the options were provided at mount time.

Existing behavior:

## Pre-existing status: debugfs is 0755.
# chmod 755 /sys/kernel/debug/
# stat -c '%A' /sys/kernel/debug/
drwxr-xr-x

## New mount sets kernel-default permissions:
# mount -t debugfs none /mnt/foo
# stat -c '%A' /mnt/foo
drwx------

## Unexpected: the original mount changed permissions:
# stat -c '%A' /sys/kernel/debug
drwx------

New behavior:

## Pre-existing status: debugfs is 0755.
# chmod 755 /sys/kernel/debug/
# stat -c '%A' /sys/kernel/debug/
drwxr-xr-x

## New mount inherits existing permissions:
# mount -t debugfs none /mnt/foo
# stat -c '%A' /mnt/foo
drwxr-xr-x

## Expected: old mount is unchanged:
# stat -c '%A' /sys/kernel/debug
drwxr-xr-x

Full test cases are being submitted to LTP.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Link: https://lore.kernel.org/r/20220912163042.v3.1.Icbd40fce59f55ad74b80e5d435ea233579348a78@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add debugfs_lookup_and_remove()

There is a very common pattern of using
debugfs_remove(debufs_lookup(..)) which results in a dentry leak of the
dentry that was looked up. Instead of having to open-code the correct
pattern of calling dput() on the dentry, create
debugfs_lookup_and_remove() to handle this pattern automatically and
properly without any memory leaks.

Cc: stable <stable@kernel.org>
Reported-by: Kuyo Chang <kuyo.chang@mediatek.com>
Tested-by: Kuyo Chang <kuyo.chang@mediatek.com>
Link: https://lore.kernel.org/r/YxIaQ8cSinDR881k@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: Document that debugfs_create functions need not be error checked

As talked about in commit b792e64021ec ("drm: no need to check return
value of debugfs_create functions"), in many cases we can get away
with totally skipping checking the errors of debugfs functions. Let's
document that so people don't add new code that needlessly checks
these errors.

Probably this note could be added to a boatload of functions, but
that's a lot of duplication. Let's just add it to the two most
frequent ones and hope people will get the idea.

Suggested-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20220222154555.1.I26d364db7a007f8995e8f0dac978673bc8e9f5e2@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: debugfs_create_file_size(): use IS_ERR to check for error

debugfs_create_file() returns encoded error so use IS_ERR for checking
return value.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Fixes: ff9fb72bc077 ("debugfs: return error values, not NULL")
Cc: stable <stable@vger.kernel.org>
References: https://gitlab.freedesktop.org/drm/amd/-/issues/1686
Link: https://lore.kernel.org/r/20210902102917.2233-1-nirmoy.das@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: fix security_locked_down() call for SELinux

When (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) is zero, then
the SELinux implementation of the locked_down hook might report a denial
even though the operation would actually be allowed.

To fix this, make sure that security_locked_down() is called only when
the return value will be taken into account (i.e. when changing one of
the problematic attributes).

Note: this was introduced by commit 5496197f9b08 ("debugfs: Restrict
debugfs when the kernel is locked down"), but it didn't matter at that
time, as the SELinux support came in later.

Fixes: 59438b46471a ("security,lockdown,selinux: implement SELinux lockdown")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Link: https://lore.kernel.org/r/20210507125304.144394-1-omosnace@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: Make debugfs_allow RO after init

Since debugfs_allow is only set at boot time during __init, make it
read-only after being set.

Fixes: a24c6f7bc923 ("debugfs: Add access restriction option")
Cc: Peter Enderborg <peter.enderborg@sony.com>
Reviewed-by: Peter Enderborg <peter.enderborg@sony.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210405213959.3079432-1-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: do not attempt to create a new file before the filesystem is initalized

Some subsystems want to add debugfs files at early boot, way before
debugfs is initialized. This seems to work somehow as the vfs layer
will not allow it to happen, but let's be explicit and test to ensure we
are properly up and running before allowing files to be created.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable <stable@vger.kernel.org>
Reported-by: Michael Walle <michael@walle.cc>
Reported-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210218100818.3622317-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: be more robust at handling improper input in debugfs_lookup()

debugfs_lookup() doesn't like it if it is passed an illegal name
pointer, or if the filesystem isn't even initialized yet. If either of
these happen, it will crash the system, so fix it up by properly testing
for valid input and that we are up and running before trying to find a
file in the filesystem.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable <stable@vger.kernel.org>
Reported-by: Michael Walle <michael@walle.cc>
Tested-by: Michael Walle <michael@walle.cc>
Tested-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210218100818.3622317-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs: make helpers idmap mount aware

Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

debugfs: Add access restriction option

Since debugfs include sensitive information it need to be treated
carefully. But it also has many very useful debug functions for userspace.
With this option we can have same configuration for system with
need of debugfs and a way to turn it off. This gives a extra protection
for exposure on systems where user-space services with system
access are attacked.

It is controlled by a configurable default value that can be override
with a kernel command line parameter. (debugfs=)

It can be on or off, but also internally on but not seen from user-space.
This no-mount mode do not register a debugfs as filesystem, but client can
register their parts in the internal structures. This data can be readed
with a debugger or saved with a crashkernel. When it is off clients
get EPERM error when accessing the functions for registering their
components.

Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
Link: https://lore.kernel.org/r/20200716071511.26864-3-peter.enderborg@sony.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: remove return value of debugfs_create_file_size()

No one checks the return value of debugfs_create_file_size, as it's not
needed, so make the return value void, so that no one tries to do so in
the future.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200309163640.237984-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: Fix warnings when building documentation

Fix the following warnings:

fs/debugfs/inode.c:423: WARNING: Inline literal start-string without end-string.
fs/debugfs/inode.c:502: WARNING: Inline literal start-string without end-string.
fs/debugfs/inode.c:534: WARNING: Inline literal start-string without end-string.
fs/debugfs/inode.c:627: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:496: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:502: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:581: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:587: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:846: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:852: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:899: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:905: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:1091: WARNING: Inline literal start-string without end-string.
fs/debugfs/file.c:1097: WARNING: Inline literal start-string without end-string

By replacing %ERR_PTR with ERR_PTR.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/20191227010035.854913-1-dwlsalmeida@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

simple_recursive_removal(): kernel-side rm -rf for ramfs-style filesystems

two requirements: no file creations in IS_DEADDIR and no cross-directory
renames whatsoever.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

new helper: lookup_positive_unlocked()

Most of the callers of lookup_one_len_unlocked() treat negatives are
ERR_PTR(-ENOENT). Provide a helper that would do just that. Note
that a pinned positive dentry remains positive - it's ->d_inode is
stable, etc.; a pinned _negative_ dentry can become positive at any
point as long as you are not holding its parent at least shared.
So using lookup_one_len_unlocked() needs to be careful;
lookup_positive_unlocked() is safer and that's what the callers
end up open-coding anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Restrict debugfs when the kernel is locked down

Disallow opening of debugfs files that might be used to muck around when
the kernel is locked down as various drivers give raw access to hardware
through debugfs. Given the effort of auditing all 2000 or so files and
manually fixing each one as necessary, I've chosen to apply a heuristic
instead. The following changes are made:

(1) chmod and chown are disallowed on debugfs objects (though the root dir
can be modified by mount and remount, but I'm not worried about that).

(2) When the kernel is locked down, only files with the following criteria
are permitted to be opened:

- The file must have mode 00444
- The file must not have ioctl methods
- The file must not have mmap

(3) When the kernel is locked down, files may only be opened for reading.

Normal device interaction should be done through configfs, sysfs or a
miscdev, not debugfs.

Note that this makes it unnecessary to specifically lock down show_dsts(),
show_devs() and show_call() in the asus-wmi driver.

I would actually prefer to lock down all files by default and have the
the files unlocked by the creator. This is tricky to manage correctly,
though, as there are 19 creation functions and ~1600 call sites (some of
them in loops scanning tables).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Andy Shevchenko <andy.shevchenko@gmail.com>
cc: acpi4asus-user@lists.sourceforge.net
cc: platform-driver-x86@vger.kernel.org
cc: Matthew Garrett <mjg59@srcf.ucam.org>
cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg KH <greg@kroah.com>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Matthew Garrett <matthewgarrett@google.com>
Signed-off-by: James Morris <jmorris@namei.org>

debugfs: make error message a bit more verbose

When a file/directory is already present in debugfs, and it is attempted
to be created again, be more specific about what file/directory is being
created and where it is trying to be created to give a bit more help to
developers to figure out the problem.

Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20190706154256.GA2683@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: provide pr_fmt() macro

Use a common "debugfs: " prefix for all pr_* calls in a single place.

Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190703071653.2799-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: log errors when something goes wrong

As it is not recommended that debugfs calls be checked, it was pointed
out that major errors should still be logged somewhere so that
developers and users have a chance to figure out what went wrong. To
help with this, error logging has been added to the debugfs core so that
it is not needed to be present in every individual file that calls
debugfs.

Reported-by: Mark Brown <broonie@kernel.org>
Reported-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190703071653.2799-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: call fsnotify_{unlink,rmdir}() hooks

This will allow generating fsnotify delete events after the
fsnotify_nameremove() hook is removed from d_delete().

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

debugfs: simplify __debugfs_remove_file()

Move simple_unlink()+d_delete() from __debugfs_remove_file() into
caller __debugfs_remove() and rename helper for post remove file to
__debugfs_file_removed().

This will simplify adding fsnotify_unlink() hook.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

debugfs: switch to ->free_inode()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

switch fsnotify_move() to passing const struct qstr * for old_name

note that in the second (RENAME_EXCHANGE) call of fsnotify_move() in
vfs_rename() the old_dentry->d_name is guaranteed to be unchanged
throughout the evaluation of fsnotify_move() (by the fact that the
parent directory is locked exclusive), so we don't need to fetch
old_dentry->d_name.name in the caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

ovl_lookup_real_one(): don't bother with strlen()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: fix use-after-free on symlink traversal

symlink body shouldn't be freed without an RCU delay. Switch debugfs to
->destroy_inode() and use of call_rcu(); free both the inode and symlink
body in the callback. Similar to solution for bpf, only here it's even
more obvious that ->evict_inode() can be dropped.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: debugfs_lookup() should return NULL if not found

Lots of callers of debugfs_lookup() were just checking NULL to see if
the file/directory was found or not. By changing this in ff9fb72bc077
("debugfs: return error values, not NULL") we caused some subsystems to
easily crash.

Fixes: ff9fb72bc077 ("debugfs: return error values, not NULL")
Reported-by: syzbot+b382ba6a802a3d242790@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: return error values, not NULL

When an error happens, debugfs should return an error pointer value, not
NULL. This will prevent the totally theoretical error where a debugfs
call fails due to lack of memory, returning NULL, and that dentry value
is then passed to another debugfs call, which would end up succeeding,
creating a file at the root of the debugfs tree, but would then be
impossible to remove (because you can not remove the directory NULL).

So, to make everyone happy, always return errors, this makes the users
of debugfs much simpler (they do not have to ever check the return
value), and everyone can rest easy.

Reported-by: Gary R Hook <ghook@amd.com>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Reported-by: Michal Hocko <mhocko@kernel.org>
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: fix debugfs_rename parameter checking

debugfs_rename() needs to check that the dentries passed into it really
are valid, as sometimes they are not (i.e. if the return value of
another debugfs call is passed into this one.) So fix this up by
properly checking if the two parent directories are errors (they are
allowed to be NULL), and if the dentry to rename is not NULL or an
error.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: debugfs_use_start/finish do not exist anymore

debugfs_use_file_start() and debugfs_use_file_finish() do not exist
since commit c9afbec27089 ("debugfs: purge obsolete SRCU based removal
protection"); tweak debugfs_create_file_unsafe() comment.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert "debugfs: inode: debugfs_create_dir uses mode permission from parent"

This reverts commit 95cde3c59966f6371b6bcd9e4e2da2ba64ee9775.

The commit had good intentions, but it breaks kvm-tool and qemu-kvm.

With it in place, "lkvm run" just fails with

Error: KVM_CREATE_VM ioctl
Warning: Failed init: kvm__init

which isn't a wonderful error message, but bisection pinpointed the
problematic commit.

The problem is almost certainly due to the special kvm debugfs entries
created dynamically by kvm under /sys/kernel/debug/kvm/. See
kvm_create_vm_debugfs()

Bisected-and-reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

debugfs: inode: debugfs_create_dir uses mode permission from parent

Currently function debugfs_create_dir() creates a new
directory in the debugfs (usually mounted /sys/kernel/debug)
with permission rwxr-xr-x. This is hard coded.

Change this to use the parent directory permission.

Output before the patch:
root@s8360047 ~]# tree -dp -L 1 /sys/kernel/debug/
/sys/kernel/debug/
├── [drwxr-xr-x] bdi
├── [drwxr-xr-x] block
├── [drwxr-xr-x] dasd
├── [drwxr-xr-x] device_component
├── [drwxr-xr-x] extfrag
├── [drwxr-xr-x] hid
├── [drwxr-xr-x] kprobes
├── [drwxr-xr-x] kvm
├── [drwxr-xr-x] memblock
├── [drwxr-xr-x] pm_qos
├── [drwxr-xr-x] qdio
├── [drwxr-xr-x] s390
├── [drwxr-xr-x] s390dbf
└── [drwx------] tracing

14 directories
[root@s8360047 linux]#

Output after the patch:
[root@s8360047 ~]# tree -dp -L 1 /sys/kernel/debug/
sys/kernel/debug/
├── [drwx------] bdi
├── [drwx------] block
├── [drwx------] dasd
├── [drwx------] device_component
├── [drwx------] extfrag
├── [drwx------] hid
├── [drwx------] kprobes
├── [drwx------] kvm
├── [drwx------] memblock
├── [drwx------] pm_qos
├── [drwx------] qdio
├── [drwx------] s390
├── [drwx------] s390dbf
└── [drwx------] tracing

14 directories
[root@s8360047 linux]#

Here is the full diff output done with:
[root@s8360047 ~]# diff -u treefull.before treefull.after |
sed 's-^- # -' > treefull.diff
# --- treefull.before 2018-04-27 13:22:04.532824564 +0200
# +++ treefull.after 2018-04-27 13:24:12.106182062 +0200
# @@ -1,55 +1,55 @@
# /sys/kernel/debug/
# -├── [drwxr-xr-x] bdi
# -│   ├── [drwxr-xr-x] 1:0
# -│   ├── [drwxr-xr-x] 1:1
# -│   ├── [drwxr-xr-x] 1:10
# -│   ├── [drwxr-xr-x] 1:11
# -│   ├── [drwxr-xr-x] 1:12
# -│   ├── [drwxr-xr-x] 1:13
# -│   ├── [drwxr-xr-x] 1:14
# -│   ├── [drwxr-xr-x] 1:15
# -│   ├── [drwxr-xr-x] 1:2
# -│   ├── [drwxr-xr-x] 1:3
# -│   ├── [drwxr-xr-x] 1:4
# -│   ├── [drwxr-xr-x] 1:5
# -│   ├── [drwxr-xr-x] 1:6
# -│   ├── [drwxr-xr-x] 1:7
# -│   ├── [drwxr-xr-x] 1:8
# -│   ├── [drwxr-xr-x] 1:9
# -│   └── [drwxr-xr-x] 94:0
# -├── [drwxr-xr-x] block
# -├── [drwxr-xr-x] dasd
# -│   ├── [drwxr-xr-x] 0.0.e18a
# -│   ├── [drwxr-xr-x] dasda
# -│   └── [drwxr-xr-x] global
# -├── [drwxr-xr-x] device_component
# -├── [drwxr-xr-x] extfrag
# -├── [drwxr-xr-x] hid
# -├── [drwxr-xr-x] kprobes
# -├── [drwxr-xr-x] kvm
# -├── [drwxr-xr-x] memblock
# -├── [drwxr-xr-x] pm_qos
# -├── [drwxr-xr-x] qdio
# -│   └── [drwxr-xr-x] 0.0.f5f2
# -├── [drwxr-xr-x] s390
# -│   └── [drwxr-xr-x] stsi
# -├── [drwxr-xr-x] s390dbf
# -│   ├── [drwxr-xr-x] 0.0.e18a
# -│   ├── [drwxr-xr-x] cio_crw
# -│   ├── [drwxr-xr-x] cio_msg
# -│   ├── [drwxr-xr-x] cio_trace
# -│   ├── [drwxr-xr-x] dasd
# -│   ├── [drwxr-xr-x] kvm-trace
# -│   ├── [drwxr-xr-x] lgr
# -│   ├── [drwxr-xr-x] qdio_0.0.f5f2
# -│   ├── [drwxr-xr-x] qdio_error
# -│   ├── [drwxr-xr-x] qdio_setup
# -│   ├── [drwxr-xr-x] qeth_card_0.0.f5f0
# -│   ├── [drwxr-xr-x] qeth_control
# -│   ├── [drwxr-xr-x] qeth_msg
# -│   ├── [drwxr-xr-x] qeth_setup
# -│   ├── [drwxr-xr-x] vmcp
# -│   └── [drwxr-xr-x] vmur
# +├── [drwx------] bdi
# +│   ├── [drwx------] 1:0
# +│   ├── [drwx------] 1:1
# +│   ├── [drwx------] 1:10
# +│   ├── [drwx------] 1:11
# +│   ├── [drwx------] 1:12
# +│   ├── [drwx------] 1:13
# +│   ├── [drwx------] 1:14
# +│   ├── [drwx------] 1:15
# +│   ├── [drwx------] 1:2
# +│   ├── [drwx------] 1:3
# +│   ├── [drwx------] 1:4
# +│   ├── [drwx------] 1:5
# +│   ├── [drwx------] 1:6
# +│   ├── [drwx------] 1:7
# +│   ├── [drwx------] 1:8
# +│   ├── [drwx------] 1:9
# +│   └── [drwx------] 94:0
# +├── [drwx------] block
# +├── [drwx------] dasd
# +│   ├── [drwx------] 0.0.e18a
# +│   ├── [drwx------] dasda
# +│   └── [drwx------] global
# +├── [drwx------] device_component
# +├── [drwx------] extfrag
# +├── [drwx------] hid
# +├── [drwx------] kprobes
# +├── [drwx------] kvm
# +├── [drwx------] memblock
# +├── [drwx------] pm_qos
# +├── [drwx------] qdio
# +│   └── [drwx------] 0.0.f5f2
# +├── [drwx------] s390
# +│   └── [drwx------] stsi
# +├── [drwx------] s390dbf
# +│   ├── [drwx------] 0.0.e18a
# +│   ├── [drwx------] cio_crw
# +│   ├── [drwx------] cio_msg
# +│   ├── [drwx------] cio_trace
# +│   ├── [drwx------] dasd
# +│   ├── [drwx------] kvm-trace
# +│   ├── [drwx------] lgr
# +│   ├── [drwx------] qdio_0.0.f5f2
# +│   ├── [drwx------] qdio_error
# +│   ├── [drwx------] qdio_setup
# +│   ├── [drwx------] qeth_card_0.0.f5f0
# +│   ├── [drwx------] qeth_control
# +│   ├── [drwx------] qeth_msg
# +│   ├── [drwx------] qeth_setup
# +│   ├── [drwx------] vmcp
# +│   └── [drwx------] vmur
# └── [drwx------] tracing
# ├── [drwxr-xr-x] events
# │   ├── [drwxr-xr-x] alarmtimer

Fixes: edac65eaf8d5c ("debugfs: take mode-dependent parts of debugfs_get_inode() into callers")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs_lookup(): switch to lookup_one_len_unlocked()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Remove redundant license text

Now that the SPDX tag is in all debugfs files, that identifies the
license in a specific and legally-defined manner. So the extra GPL text
wording can be removed as it is no longer needed at all.

This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text. And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.

No copyright headers or other non-license-description text was removed.

Cc: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add SPDX identifiers to all debugfs files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the debugfs files files with the correct SPDX license identifier
based on the license text in the file itself. The SPDX identifier is a
legally binding shorthand, which can be used instead of the full boiler
plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: defer debugfs_fsdata allocation to first usage

Currently, __debugfs_create_file allocates one struct debugfs_fsdata
instance for every file created. However, there are potentially many
debugfs file around, most of which are never touched by userspace.

Thus, defer the allocations to the first usage, i.e. to the first
debugfs_file_get().

A dentry's ->d_fsdata starts out to point to the "real", user provided
fops. After a debugfs_fsdata instance has been allocated (and the real
fops pointer has been moved over into its ->real_fops member),
->d_fsdata is changed to point to it from then on. The two cases are
distinguished by setting BIT(0) for the real fops case.

struct debugfs_fsdata's foremost purpose is to track active users and to
make debugfs_remove() block until they are done. Since no debugfs_fsdata
instance means no active users, make debugfs_remove() return immediately
in this case.

Take care of possible races between debugfs_file_get() and
debugfs_remove(): either debugfs_remove() must see a debugfs_fsdata
instance and thus wait for possible active users or debugfs_file_get() must
see a dead dentry and return immediately.

Make a dentry's ->d_release(), i.e. debugfs_release_dentry(), check whether
->d_fsdata is actually a debugfs_fsdata instance before kfree()ing it.

Similarly, make debugfs_real_fops() check whether ->d_fsdata is actually
a debugfs_fsdata instance before returning it, otherwise emit a warning.

The set of possible error codes returned from debugfs_file_get() has grown
from -EIO to -EIO and -ENOMEM. Make open_proxy_open() and full_proxy_open()
pass the -ENOMEM onwards to their callers.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: purge obsolete SRCU based removal protection

Purge the SRCU based file removal race protection in favour of the new,
refcount based debugfs_file_get()/debugfs_file_put() API.

Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: implement per-file removal protection

Since commit 49d200deaa68 ("debugfs: prevent access to removed files'
private data"), accesses to a file's private data are protected from
concurrent removal by covering all file_operations with a SRCU read section
and sychronizing with those before returning from debugfs_remove() by means
of synchronize_srcu().

As pointed out by Johannes Berg, there are debugfs files with forever
blocking file_operations. Their corresponding SRCU read side sections would
block any debugfs_remove() forever as well, even unrelated ones. This
results in a livelock. Because a remover can't cancel any indefinite
blocking within foreign files, this is a problem.

Resolve this by introducing support for more granular protection on a
per-file basis.

This is implemented by introducing an 'active_users' refcount_t to the
per-file struct debugfs_fsdata state. At file creation time, it is set to
one and a debugfs_remove() will drop that initial reference. The new
debugfs_file_get() and debugfs_file_put(), intended to be used in place of
former debugfs_use_file_start() and debugfs_use_file_finish(), increment
and decrement it respectively. Once the count drops to zero,
debugfs_file_put() will signal a completion which is possibly being waited
for from debugfs_remove().
Thus, as long as there is a debugfs_file_get() not yet matched by a
corresponding debugfs_file_put() around, debugfs_remove() will block.

Actual users of debugfs_use_file_start() and -finish() will get converted
to the new debugfs_file_get() and debugfs_file_put() by followup patches.

Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data")
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add support for more elaborate ->d_fsdata

Currently, the user provided fops, "real_fops", are stored directly into
->d_fsdata.

In order to be able to store more per-file state and thus prepare for more
granular file removal protection, wrap the real_fops into a dynamically
allocated container struct, debugfs_fsdata.

A struct debugfs_fsdata gets allocated at file creation and freed from the
newly intoduced ->d_release().

Finally, move the implementation of debugfs_real_fops() out of the public
debugfs header such that struct debugfs_fsdata's declaration can be kept
private.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

dentry name snapshots

take_dentry_name_snapshot() takes a safe snapshot of dentry name;
if the name is a short one, it gets copied into caller-supplied
structure, otherwise an extra reference to external name is grabbed
(those are never modified). In either case the pointer to stable
string is stored into the same structure.

dentry must be held by the caller of take_dentry_name_snapshot(),
but may be freely dropped afterwards - the snapshot will stay
until destroyed by release_dentry_name_snapshot().

Intended use:
struct name_snapshot s;

take_dentry_name_snapshot(&s, dentry);
...
access s.name
...
release_dentry_name_snapshot(&s);

Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name
to pass down with event.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

VFS: Don't use save/replace_mount_options if not using generic_show_options

btrfs, debugfs, reiserfs and tracefs call save_mount_options() and reiserfs
calls replace_mount_options(), but they then implement their own
->show_options() methods and don't touch s_options, rendering the saved
options unnecessary. I'm trying to eliminate s_options to make it easier
to implement a context-based mount where the mount options can be passed
individually over a file descriptor.

Remove the calls to save/replace_mount_options() call in these cases.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Chris Mason <clm@fb.com>
cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: Steven Rostedt <rostedt@goodmis.org>
cc: linux-btrfs@vger.kernel.org
cc: reiserfs-devel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs: fix the location of the kernel-api book

The kernel-api book is now part of the core-api. Update its
location.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

fs: constify tree_descr arrays passed to simple_fill_super()

simple_fill_super() is passed an array of tree_descr structures which
describe the files to create in the filesystem's root directory. Since
these arrays are never modified intentionally, they should be 'const' so
that they are placed in .rodata and benefit from memory protection.
This patch updates the function signature and all users, and also
constifies tree_descr.name.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: add debugfs_lookup()

We don't always have easy access to the dentry of a file or directory we
created in debugfs. Add a helper which allows us to get a dentry we
previously created.

The motivation for this change is a problem with blktrace and the blk-mq
debugfs entries introduced in 07e4fead45e6 ("blk-mq: create debugfs
directory tree"). Namely, in some cases, the directory that blktrace
needs to create may already exist, but in other cases, it may not. We
_could_ rely on a bunch of implied knowledge to decide whether to create
the directory or not, but it's much cleaner on our end to just look it
up.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

fs: Better permission checking for submounts

To support unprivileged users mounting filesystems two permission
checks have to be performed: a test to see if the user allowed to
create a mount in the mount namespace, and a test to see if
the user is allowed to access the specified filesystem.

The automount case is special in that mounting the original filesystem
grants permission to mount the sub-filesystems, to any user who
happens to stumble across the their mountpoint and satisfies the
ordinary filesystem permission checks.

Attempting to handle the automount case by using override_creds
almost works. It preserves the idea that permission to mount
the original filesystem is permission to mount the sub-filesystem.
Unfortunately using override_creds messes up the filesystems
ordinary permission checks.

Solve this by being explicit that a mount is a submount by introducing
vfs_submount, and using it where appropriate.

vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let
sget and friends know that a mount is a submount so they can take appropriate
action.

sget and sget_userns are modified to not perform any permission checks
on submounts.

follow_automount is modified to stop using override_creds as that
has proven problemantic.

do_mount is modified to always remove the new MS_SUBMOUNT flag so
that we know userspace will never by able to specify it.

autofs4 is modified to stop using current_real_cred that was put in
there to handle the previous version of submount permission checking.

cifs is modified to pass the mountpoint all of the way down to vfs_submount.

debugfs is modified to pass the mountpoint all of the way down to
trace_automount by adding a new parameter. To make this change easier
a new typedef debugfs_automount_t is introduced to capture the type of
the debugfs automount function.

Cc: stable@vger.kernel.org
Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid")
Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds")
Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

fs: Replace current_fs_time() with current_time()

current_fs_time() uses struct super_block* as an argument.
As per Linus's suggestion, this is changed to take struct
inode* as a parameter instead. This is because the function
is primarily meant for vfs inode timestamps.
Also the function was renamed as per Arnd's suggestion.

Change all calls to current_fs_time() to use the new
current_time() function instead. current_fs_time() will be
deleted.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

libfs: support RENAME_NOREPLACE in simple_rename()

This is trivial to do:

- add flags argument to simple_rename()
- check if flags doesn't have any other than RENAME_NOREPLACE
- assign simple_rename() to .rename2 instead of .rename

Filesystems converted:

hugetlbfs, ramfs, bpf.

Debugfs uses simple_rename() to implement debugfs_rename(), which is for
debugfs instances to rename files internally, not for userspace filesystem
access. For this case pass zero flags to simple_rename().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>

debugfs: ->d_parent is never NULL or negative

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Make automount point inodes permanently empty

Starting with 4.1 the tracing subsystem has its own filesystem
which is automounted in the tracing subdirectory of debugfs.
Prior to this debugfs could be bind mounted in a cloned mount
namespace, but if tracefs has been mounted under debugfs this
now fails because there is a locked child mount. This creates
a regression for container software which bind mounts debugfs
to satisfy the assumption of some userspace software.

In other pseudo filesystems such as proc and sysfs we're already
creating mountpoints like this in such a way that no dirents can
be created in the directories, allowing them to be exceptions to
some MNT_LOCKED tests. In fact we're already do this for the
tracefs mountpoint in sysfs.

Do the same in debugfs_create_automount(), since the intention
here is clearly to create a mountpoint. This fixes the regression,
as locked child mounts on permanently empty directories do not
cause a bind mount to fail.

Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add support for self-protecting attribute file fops

In order to protect them against file removal issues, debugfs_create_file()
creates a lifetime managing proxy around each struct file_operations
handed in.

In cases where this struct file_operations is able to manage file lifetime
by itself already, the proxy created by debugfs is a waste of resources.

The most common class of struct file_operations given to debugfs are those
defined by means of the DEFINE_SIMPLE_ATTRIBUTE() macro.

Introduce a DEFINE_DEBUGFS_ATTRIBUTE() macro to allow any
struct file_operations of this class to be easily made file lifetime aware
and thus, to be operated unproxied.

Specifically, introduce debugfs_attr_read() and debugfs_attr_write()
which wrap simple_attr_read() and simple_attr_write() under the protection
of a debugfs_use_file_start()/debugfs_use_file_finish() pair.

Make DEFINE_DEBUGFS_ATTRIBUTE() set the defined struct file_operations'
->read() and ->write() members to these wrappers.

Export debugfs_create_file_unsafe() in order to allow debugfs users to
create their files in non-proxying operation mode.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: prevent access to removed files' private data

Upon return of debugfs_remove()/debugfs_remove_recursive(), it might
still be attempted to access associated private file data through
previously opened struct file objects. If that data has been freed by
the caller of debugfs_remove*() in the meanwhile, the reading/writing
process would either encounter a fault or, if the memory address in
question has been reassigned again, unrelated data structures could get
overwritten.

However, since debugfs files are seldomly removed, usually from module
exit handlers only, the impact is very low.

Currently, there are ~1000 call sites of debugfs_create_file() spread
throughout the whole tree and touching all of those struct file_operations
in order to make them file removal aware by means of checking the result of
debugfs_use_file_start() from within their methods is unfeasible.

Instead, wrap the struct file_operations by a lifetime managing proxy at
file open:
- In debugfs_create_file(), the original fops handed in has got stashed
away in ->d_fsdata already.
- In debugfs_create_file(), install a proxy file_operations factory,
debugfs_full_proxy_file_operations, at ->i_fop.

This proxy factory has got an ->open() method only. It carries out some
lifetime checks and if successful, dynamically allocates and sets up a new
struct file_operations proxy at ->f_op. Afterwards, it forwards to the
->open() of the original struct file_operations in ->d_fsdata, if any.

The dynamically set up proxy at ->f_op has got a lifetime managing wrapper
set for each of the methods defined in the original struct file_operations
in ->d_fsdata.

Its ->release()er frees the proxy again and forwards to the original
->release(), if any.

In order not to mislead the VFS layer, it is strictly necessary to leave
those fields blank in the proxy that have been NULL in the original
struct file_operations also, i.e. aren't supported. This is why there is a
need for dynamically allocated proxies. The choice made not to allocate a
proxy instance for every dentry at file creation, but for every
struct file object instantiated thereof is justified by the expected usage
pattern of debugfs, namely that in general very few files get opened more
than once at a time.

The wrapper methods set in the struct file_operations implement lifetime
managing by means of the SRCU protection facilities already in place for
debugfs:
They set up a SRCU read side critical section and check whether the dentry
is still alive by means of debugfs_use_file_start(). If so, they forward
the call to the original struct file_operation stored in ->d_fsdata, still
under the protection of the SRCU read side critical section.
This SRCU read side critical section prevents any pending debugfs_remove()
and friends to return to their callers. Since a file's private data must
only be freed after the return of debugfs_remove(), the ongoing proxied
call is guarded against any file removal race.

If, on the other hand, the initial call to debugfs_use_file_start() detects
that the dentry is dead, the wrapper simply returns -EIO and does not
forward the call. Note that the ->poll() wrapper is special in that its
signature does not allow for the return of arbitrary -EXXX values and thus,
POLLHUP is returned here.

In order not to pollute debugfs with wrapper definitions that aren't ever
needed, I chose not to define a wrapper for every struct file_operations
method possible. Instead, a wrapper is defined only for the subset of
methods which are actually set by any debugfs users.
Currently, these are:

->llseek()
->read()
->write()
->unlocked_ioctl()
->poll()

The ->release() wrapper is special in that it does not protect the original
->release() in any way from dead files in order not to leak resources.
Thus, any ->release() handed to debugfs must implement file lifetime
management manually, if needed.
For only 33 out of a total of 434 releasers handed in to debugfs, it could
not be verified immediately whether they access data structures that might
have been freed upon a debugfs_remove() return in the meanwhile.

Export debugfs_use_file_start() and debugfs_use_file_finish() in order to
allow any ->release() to manually implement file lifetime management.

For a set of common cases of struct file_operations implemented by the
debugfs_core itself, future patches will incorporate file lifetime
management directly within those in order to allow for their unproxied
operation. Rename the original, non-proxying "debugfs_create_file()" to
"debugfs_create_file_unsafe()" and keep it for future internal use by
debugfs itself. Factor out code common to both into the new
__debugfs_create_file().

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: prevent access to possibly dead file_operations at file open

Nothing prevents a dentry found by path lookup before a return of
__debugfs_remove() to actually get opened after that return. Now, after
the return of __debugfs_remove(), there are no guarantees whatsoever
regarding the memory the corresponding inode's file_operations object
had been kept in.

Since __debugfs_remove() is seldomly invoked, usually from module exit
handlers only, the race is hard to trigger and the impact is very low.

A discussion of the problem outlined above as well as a suggested
solution can be found in the (sub-)thread rooted at

http://lkml.kernel.org/g/20130401203445.GA20862@ZenIV.linux.org.uk
("Yet another pipe related oops.")

Basically, Greg KH suggests to introduce an intermediate fops and
Al Viro points out that a pointer to the original ones may be stored in
->d_fsdata.

Follow this line of reasoning:
- Add SRCU as a reverse dependency of DEBUG_FS.
- Introduce a srcu_struct object for the debugfs subsystem.
- In debugfs_create_file(), store a pointer to the original
file_operations object in ->d_fsdata.
- Make debugfs_remove() and debugfs_remove_recursive() wait for a
SRCU grace period after the dentry has been delete()'d and before they
return to their callers.
- Introduce an intermediate file_operations object named
"debugfs_open_proxy_file_operations". It's ->open() functions checks,
under the protection of a SRCU read lock, whether the dentry is still
alive, i.e. has not been d_delete()'d and if so, tries to acquire a
reference on the owning module.
On success, it sets the file object's ->f_op to the original
file_operations and forwards the ongoing open() call to the original
->open().
- For clarity, rename the former debugfs_file_operations to
debugfs_noop_file_operations -- they are in no way canonical.

The choice of SRCU over "normal" RCU is justified by the fact, that the
former may also be used to protect ->i_private data from going away
during the execution of a file's readers and writers which may (and do)
sleep.

Finally, introduce the fs/debugfs/internal.h header containing some
declarations internal to the debugfs implementation.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs: debugfs: Replace CURRENT_TIME by current_fs_time()

CURRENT_TIME macro is not appropriate for filesystems as it
doesn't use the right granularity for filesystem timestamps.
Use current_fs_time() instead.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: fix inode i_nlink references for automount dentry

Directory inodes should start off with i_nlink == 2 (one extra ref
for "." entry). debugfs_create_automount() increases neither the
i_nlink reference for current inode nor for parent inode.

On attempt to remove the automount dentry, kernel complains:

[ 86.288070] WARNING: CPU: 1 PID: 3616 at fs/inode.c:273 drop_nlink+0x3e/0x50()
[ 86.288461] Modules linked in: debugfs_example2(O-)
[ 86.288745] CPU: 1 PID: 3616 Comm: rmmod Tainted: G O 4.4.0-rc3-next-20151207+ #135
[ 86.289197] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150617_082717-anatol 04/01/2014
[ 86.289696] ffffffff81be05c9 ffff8800b9e6fda0 ffffffff81352e2c 0000000000000000
[ 86.290110] ffff8800b9e6fdd8 ffffffff81065142 ffff8801399175e8 ffff8800bb78b240
[ 86.290507] ffff8801399175e8 ffff8800b73d7898 ffff8800b73d7840 ffff8800b9e6fde8
[ 86.290933] Call Trace:
[ 86.291080] [<ffffffff81352e2c>] dump_stack+0x4e/0x82
[ 86.291340] [<ffffffff81065142>] warn_slowpath_common+0x82/0xc0
[ 86.291640] [<ffffffff8106523a>] warn_slowpath_null+0x1a/0x20
[ 86.291932] [<ffffffff811ae62e>] drop_nlink+0x3e/0x50
[ 86.292208] [<ffffffff811ba35b>] simple_unlink+0x4b/0x60
[ 86.292481] [<ffffffff811ba3a7>] simple_rmdir+0x37/0x50
[ 86.292748] [<ffffffff812d9808>] __debugfs_remove.part.16+0xa8/0xd0
[ 86.293082] [<ffffffff812d9a0b>] debugfs_remove_recursive+0xdb/0x1c0
[ 86.293406] [<ffffffffa00004dd>] cleanup_module+0x2d/0x3b [debugfs_example2]
[ 86.293762] [<ffffffff810d959b>] SyS_delete_module+0x16b/0x220
[ 86.294077] [<ffffffff818ef857>] entry_SYSCALL_64_fastpath+0x12/0x6a
[ 86.294405] ---[ end trace c9fc53353fe14a36 ]---
[ 86.294639] ------------[ cut here ]------------

To reproduce the issue it is enough to invoke these lines:

autom = debugfs_create_automount("automount", NULL, vfsmount_cb, data);
BUG_ON(IS_ERR_OR_NULL(autom));
debugfs_remove(autom);

The issue is fixed by increasing inode i_nlink references for current
and parent inodes.

Signed-off-by: Roman Pen <r.peniaev@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: fix refcount imbalance in start_creating

In debugfs' start_creating(), we pin the file system to safely access
its root. When we failed to create a file, we unpin the file system via
failed_creating() to release the mount count and eventually the reference
of the vfsmount.

However, when we run into an error during lookup_one_len() when still
in start_creating(), we only release the parent's mutex but not so the
reference on the mount. Looks like it was done in the past, but after
splitting portions of __create_file() into start_creating() and
end_creating() via 190afd81e4a5 ("debugfs: split the beginning and the
end of __create_file() off"), this seemed missed. Noticed during code
review.

Fixes: 190afd81e4a5 ("debugfs: split the beginning and the end of __create_file() off")
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: document that debugfs_remove*() accepts NULL and error values

According to commit a59d6293e537 ("debugfs: change parameter check in
debugfs_remove() functions"), this is meant to make cleanup easier for
callers. In that case it ought to be documented.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: document that debugfs_remove*() accepts NULL and error values

According to commit a59d6293e537 ("debugfs: change parameter check in
debugfs_remove() functions"), this is meant to make cleanup easier for
callers. In that case it ought to be documented.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

sysfs: Create mountpoints with sysfs_create_mount_point

This allows for better documentation in the code and
it allows for a simpler and fully correct version of
fs_fully_visible to be written.

The mount points converted and their filesystems are:
/sys/hypervisor/s390/ s390_hypfs
/sys/kernel/config/ configfs
/sys/kernel/debug/ debugfs
/sys/firmware/efi/efivars/ efivarfs
/sys/fs/fuse/connections/ fusectl
/sys/fs/pstore/ pstore
/sys/kernel/tracing/ tracefs
/sys/fs/cgroup/ cgroup
/sys/kernel/security/ securityfs
/sys/fs/selinux/ selinuxfs
/sys/fs/smackfs/ smackfs

Cc: stable@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

make simple_positive() public

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: switch to simple_follow_link()

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

VFS: normal filesystems (and lustre): d_inode() annotations

that's the bulk of filesystem drivers dealing with inodes of their own

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

VFS: Fix up debugfs to use d_is_dir() in place of S_ISDIR()

Fix up debugfs to use d_is_dir(dentry) in place of
S_ISDIR(dentry->d_inode->i_mode).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: allow bad parent pointers to be passed in

If something went wrong with creating a debugfs file/symlink/directory,
that value could be passed down into debugfs again as a parent dentry.
To make caller code simpler, just error out if this happens, and don't
crash the kernel.

Reported-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alex Elder <elder@linaro.org>

debugfs: leave freeing a symlink body until inode eviction

As it is, we have debugfs_remove() racing with symlink traversals.
Supply ->evict_inode() and do freeing there - inode will remain
pinned until we are done with the symlink body.

And rip the idiocy with checking if dentry is positive right after
we'd verified debugfs_positive(), which is a stronger check...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry)

Convert the following where appropriate:

(1) S_ISLNK(dentry->d_inode) to d_is_symlink(dentry).

(2) S_ISREG(dentry->d_inode) to d_is_reg(dentry).

(3) S_ISDIR(dentry->d_inode) to d_is_dir(dentry). This is actually more
complicated than it appears as some calls should be converted to
d_can_lookup() instead. The difference is whether the directory in
question is a real dir with a ->lookup op or whether it's a fake dir with
a ->d_automount op.

In some circumstances, we can subsume checks for dentry->d_inode not being
NULL into this, provided we the code isn't in a filesystem that expects
d_inode to be NULL if the dirent really *is* negative (ie. if we're going to
use d_inode() rather than d_backing_inode() to get the inode pointer).

Note that the dentry type field may be set to something other than
DCACHE_MISS_TYPE when d_inode is NULL in the case of unionmount, where the VFS
manages the fall-through from a negative dentry to a lower layer. In such a
case, the dentry type of the negative union dentry is set to the same as the
type of the lower dentry.

However, if you know d_inode is not NULL at the call site, then you can use
the d_is_xxx() functions even in a filesystem.

There is one further complication: a 0,0 chardev dentry may be labelled
DCACHE_WHITEOUT_TYPE rather than DCACHE_SPECIAL_TYPE. Strictly, this was
intended for special directory entry types that don't have attached inodes.

The following perl+coccinelle script was used:

use strict;

my @callers;
open($fd, 'git grep -l \'S_IS[A-Z].*->d_inode\' |') ||
die "Can't grep for S_ISDIR and co. callers";
@callers = <$fd>;
close($fd);
unless (@callers) {
print "No matches\n";
exit(0);
}

my @cocci = (
'@@',
'expression E;',
'@@',
'',
'- S_ISLNK(E->d_inode->i_mode)',
'+ d_is_symlink(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISDIR(E->d_inode->i_mode)',
'+ d_is_dir(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISREG(E->d_inode->i_mode)',
'+ d_is_reg(E)' );

my $coccifile = "tmp.sp.cocci";
open($fd, ">$coccifile") || die $coccifile;
print($fd "$_\n") || die $coccifile foreach (@cocci);
close($fd);

foreach my $file (@callers) {
chomp $file;
print "Processing ", $file, "\n";
system("spatch", "--sp-file", $coccifile, $file, "--in-place", "--no-show-diff") == 0 ||
die "spatch failed";
}

[AV: overlayfs parts skipped]

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Provide a file creation function that also takes an initial size

Provide a file creation function that also takes an initial size so that the
caller doesn't have to set i_size, thus meaning that we don't have to call
deal with ->d_inode in the callers.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Provide a file creation function that also takes an initial size

Provide a file creation function that also takes an initial size so that the
caller doesn't have to set i_size, thus meaning that we don't have to call
deal with ->d_inode in the callers.

Signed-off-by: David Howells <dhowells@redhat.com>

new primitive: debugfs_create_automount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: split end_creating() into success and failure cases

... and don't bother with dput(dentry) in the former and with
dget(dentry) preceding all its calls.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: take mode-dependent parts of debugfs_get_inode() into callers

... and trim the arguments list

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fold debugfs_mknod() into callers

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fold debugfs_create() into caller

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fold debugfs_mkdir() into caller

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs_mknod(): get rid useless arguments

dev is always zero, dir was only used to get its ->i_sb, which is
equal to ->d_sb of dentry...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fold debugfs_link() into caller

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: kill __create_file()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: split the beginning and the end of __create_file() off

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs_{mkdir,create,link}(): get rid of redundant argument

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

move d_rcu from overlapping d_child to overlapping d_alias

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs: debugfs: remove trailing whitespace

fixes checkpatch.pl trailing whitespace errors

Signed-off-by: Rahul Bedarkar <rahulbedarkar89@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: Fix corrupted loop in debugfs_remove_recursive

[ I'm currently running my tests on it now, and so far, after a few
hours it has yet to blow up. I'll run it for 24 hours which it never
succeeded in the past. ]

The tracing code has a way to make directories within the debugfs file
system as well as deleting them using mkdir/rmdir in the instance
directory. This is very limited in functionality, such as there is
no renames, and the parent directory "instance" can not be modified.
The tracing code creates the instance directory from the debugfs code
and then replaces the dentry->d_inode->i_op with its own to allow
for mkdir/rmdir to work.

When these are called, the d_entry and inode locks need to be released
to call the instance creation and deletion code. That code has its own
accounting and locking to serialize everything to prevent multiple
users from causing harm. As the parent "instance" directory can not
be modified this simplifies things.

I created a stress test that creates several threads that randomly
creates and deletes directories thousands of times a second. The code
stood up to this test and I submitted it a while ago.

Recently I added a new test that adds readers to the mix. While the
instance directories were being added and deleted, readers would read
from these directories and even enable tracing within them. This test
was able to trigger a bug:

general protection fault: 0000 [#1] PREEMPT SMP
Modules linked in: ...
CPU: 3 PID: 17789 Comm: rmdir Tainted: G W 3.15.0-rc2-test+ #41
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
task: ffff88003786ca60 ti: ffff880077018000 task.ti: ffff880077018000
RIP: 0010:[<ffffffff811ed5eb>] [<ffffffff811ed5eb>] debugfs_remove_recursive+0x1bd/0x367
RSP: 0018:ffff880077019df8 EFLAGS: 00010246
RAX: 0000000000000002 RBX: ffff88006f0fe490 RCX: 0000000000000000
RDX: dead000000100058 RSI: 0000000000000246 RDI: ffff88003786d454
RBP: ffff88006f0fe640 R08: 0000000000000628 R09: 0000000000000000
R10: 0000000000000628 R11: ffff8800795110a0 R12: ffff88006f0fe640
R13: ffff88006f0fe640 R14: ffffffff81817d0b R15: ffffffff818188b7
FS: 00007ff13ae24700(0000) GS:ffff88007d580000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000003054ec7be0 CR3: 0000000076d51000 CR4: 00000000000007e0
Stack:
ffff88007a41ebe0 dead000000100058 00000000fffffffe ffff88006f0fe640
0000000000000000 ffff88006f0fe678 ffff88007a41ebe0 ffff88003793a000
00000000fffffffe ffffffff810bde82 ffff88006f0fe640 ffff88007a41eb28
Call Trace:
[<ffffffff810bde82>] ? instance_rmdir+0x15b/0x1de
[<ffffffff81132e2d>] ? vfs_rmdir+0x80/0xd3
[<ffffffff81132f51>] ? do_rmdir+0xd1/0x139
[<ffffffff8124ad9e>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[<ffffffff814fea62>] ? system_call_fastpath+0x16/0x1b
Code: fe ff ff 48 8d 75 30 48 89 df e8 c9 fd ff ff 85 c0 75 13 48 c7 c6 b8 cc d2 81 48 c7 c7 b0 cc d2 81 e8 8c 7a f5 ff 48 8b 54 24 08 <48> 8b 82 a8 00 00 00 48 89 d3 48 2d a8 00 00 00 48 89 44 24 08
RIP [<ffffffff811ed5eb>] debugfs_remove_recursive+0x1bd/0x367
RSP <ffff880077019df8>

It took a while, but every time it triggered, it was always in the
same place:

list_for_each_entry_safe(child, next, &parent->d_subdirs, d_u.d_child) {

Where the child->d_u.d_child seemed to be corrupted. I added lots of
trace_printk()s to see what was wrong, and sure enough, it was always
the child's d_u.d_child field. I looked around to see what touches
it and noticed that in __dentry_kill() which calls dentry_free():

static void dentry_free(struct dentry *dentry)
{
/* if dentry was never visible to RCU, immediate free is OK */
if (!(dentry->d_flags & DCACHE_RCUACCESS))
__d_free(&dentry->d_u.d_rcu);
else
call_rcu(&dentry->d_u.d_rcu, __d_free);
}

I also noticed that __dentry_kill() unlinks the child->d_u.child
under the parent->d_lock spin_lock.

Looking back at the loop in debugfs_remove_recursive() it never takes the
parent->d_lock to do the list walk. Adding more tracing, I was able to
prove this was the issue:

ftrace-t-15385 1.... 246662024us : dentry_kill <ffffffff81138b91>: free ffff88006d573600
rmdir-15409 2.... 246662024us : debugfs_remove_recursive <ffffffff811ec7e5>: child=ffff88006d573600 next=dead000000100058

The dentry_kill freed ffff88006d573600 just as the remove recursive was walking
it.

In order to fix this, the list walk needs to be modified a bit to take
the parent->d_lock. The safe version is no longer necessary, as every
time we remove a child, the parent->d_lock must be released and the
list walk must start over. Each time a child is removed, even though it
may still be on the list, it should be skipped by the first check
in the loop:

if (!debugfs_positive(child))
continue;

Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs: push sync_filesystem() down to the file system's remount_fs()

Previously, the no-op "mount -o mount /dev/xxx" operation when the
file system is already mounted read-write causes an implied,
unconditional syncfs(). This seems pretty stupid, and it's certainly
documented or guaraunteed to do this, nor is it particularly useful,
except in the case where the file system was mounted rw and is getting
remounted read-only.

However, it's possible that there might be some file systems that are
actually depending on this behavior. In most file systems, it's
probably fine to only call sync_filesystem() when transitioning from
read-write to read-only, and there are some file systems where this is
not needed at all (for example, for a pseudo-filesystem or something
like romfs).

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Jan Kara <jack@suse.cz>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Anders Larsen <al@alarsen.net>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: Petr Vandrovec <petr@vandrovec.name>
Cc: xfs@oss.sgi.com
Cc: linux-btrfs@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: codalist@coda.cs.cmu.edu
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: fuse-devel@lists.sourceforge.net
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: linux-nilfs@vger.kernel.org
Cc: linux-ntfs-dev@lists.sourceforge.net
Cc: ocfs2-devel@oss.oracle.com
Cc: reiserfs-devel@vger.kernel.org

treewide: Fix typo in Documentation/DocBook

This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

debugfs: use list_next_entry() in debugfs_remove_recursive()

Change debugfs_remove_recursive() to use list_next_entry(child), no
changes in generated code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

debugfs: debugfs_remove_recursive() must not rely on list_empty(d_subdirs)

debugfs_remove_recursive() is wrong,

1. it wrongly assumes that !list_empty(d_subdirs) means that this
dir should be removed.

This is not that bad by itself, but:

2. if d_subdirs does not becomes empty after __debugfs_remove()
it gives up and silently fails, it doesn't even try to remove
other entries.

However ->d_subdirs can be non-empty because it still has the
already deleted !debugfs_positive() entries.

3. simple_release_fs() is called even if __debugfs_remove() fails.

Suppose we have

dir1/
dir2/
file2
file1

and someone opens dir1/dir2/file2.

Now, debugfs_remove_recursive(dir1/dir2) succeeds, and dir1/dir2 goes
away.

But debugfs_remove_recursive(dir1) silently fails and doesn't remove
this directory. Because it tries to delete (the already deleted)
dir1/dir2/file2 again and then fails due to "Avoid infinite loop"
logic.

Test-case:

#!/bin/sh

cd /sys/kernel/debug/tracing
echo 'p:probe/sigprocmask sigprocmask' >> kprobe_events
sleep 1000 < events/probe/sigprocmask/id &
echo -n >| kprobe_events

[ -d events/probe ] && echo "ERR!! failed to rm probe"

And after that it is not possible to create another probe entry.

With this patch debugfs_remove_recursive() skips !debugfs_positive()
files although this is not strictly needed. The most important change
is that it does not try to make ->d_subdirs empty, it simply scans
the whole list(s) recursively and removes as much as possible.

Link: http://lkml.kernel.org/r/20130726151256.GC19472@redhat.com

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

fs: Limit sys_mount to only request filesystem modules.

Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives. Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work. While writing this patch I saw a handful of such
cases. The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module. The common pattern in the kernel is to call request_module()
without regards to the users permissions. In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted. In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

debugfs: remove redundant initialization of dentry

We already initialize it to NULL when declaring it, no need to do
that twice.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: convert gid= argument from decimal, not octal

This patch technically breaks userspace, but I suspect that anyone who
actually used this flag would have encountered this brokenness, declared
it lunacy, and already sent a patch.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>
Reviewed-by: Vasiliy Kulikov <segoon@openwall.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/debugsfs: remove unnecessary inode->i_private initialization

inode->i_private is promised to be NULL on allocation, no need to set it
explicitly.

Signed-off-by: Yan Hong <clouds.yan@gmail.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

userns: Convert debugfs to use kuid/kgid where appropriate.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

debugfs: more tightly restrict default mount mode

Since the debugfs is mostly only used by root, make the default mount
mode 0700. Most system owners do not need a more permissive value,
but they can choose to weaken the restrictions via their fstab.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: make __create_file static

It's only used locally, no need to pollute global namespace.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: get rid of useless arguments to debugfs_{mkdir,symlink}

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: fold debugfs_create_by_name() into the only caller

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: make sure that debugfs_create_file() gets used only for regulars

It, debugfs_create_dir() and debugfs_create_link() use the common helper
now.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: change parameter check in debugfs_remove() functions

The dentry parameter in debugfs_remove() and debugfs_remove_recursive()
is checked being a NULL pointer. To make cleanup by callers easier this
check is extended using the IS_ERR_OR_NULL macro instead because the
debugfs_create_... functions can return a ERR_PTR() value.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

debugfs: add mode, uid and gid options

Cautious admins may want to restrict access to debugfs. Currently a
manual chown/chmod e.g. in an init script is needed to achieve that.
Distributions that want to make the mount options configurable need
to add extra config files. By allowing to set the root inode's uid,
gid and mode via mount options no such hacks are needed anymore.
Instead configuration becomes straight forward via fstab.

Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

switch debugfs to umode_t

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs: for usbfs, etc. internal vfsmounts ->mnt_sb->s_root == ->mnt_root

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: Fix a comment mistake

The file is fs/debugfs/inode.c but the comment says it is file.c.
This patch can fix this little mistake.

Signed-off-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: Fix filesystem reference counting on debugfs_remove() failure

When __debugfs_remove() fails (because simple_rmdir() fails e.g. when a
directory is not empty), we must not decrement use count of the filesystem
as nothing was in fact deleted.

This fixes use after free caused by debugfs in some cases.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: remove module_exit()

debugfs can't be a module, so module_exit() is meaningless for it.

Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

convert get_sb_single() users

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs: do not assign default i_ino in new_inode

Instead of always assigning an increasing inode number in new_inode
move the call to assign it into those callers that actually need it.
For now callers that need it is estimated conservatively, that is
the call is added to all filesystems that do not assign an i_ino
by themselves. For a few more filesystems we can avoid assigning
any inode number given that they aren't user visible, and for others
it could be done lazily when an inode number is actually needed,
but that's left for later patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.

2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).

* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

Lose the new_name argument of fsnotify_move()

it's always new_dentry->d_name.name

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

get rid of pointless checks after simple_pin_fs()

if we'd just got success from it, vfsmount won't be NULL

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: fix create mutex racy fops and private data

Setting fops and private data outside of the mutex at debugfs file
creation introduces a race where the files can be opened with the wrong
file operations and private data. It is easy to trigger with a process
waiting on file creation notification.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/debugfs/inode.c: fix comment typos

Signed-off-by: Alberto Bertogli <albertito@blitiri.com.ar>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

debugfs: dont stop on first failed recursive delete

debugfs: dont stop on first failed recursive delete

While running a while loop of removing a module that removes a debugfs
directory with debugfs_remove_recursive, and at the same time doing a
while loop of cat of a file in that directory, I would hit a point where
somehow the cat of the file caused the remove to fail.

The result is that other files did not get removed when the module
was removed. I simple read of one of those file can oops the kernel
because the operations to the file no longer exist (removed by module).

The funny thing is that the file being cat'ed was removed. It was
the siblings that were not. I see in the code to debugfs_remove_recursive
there's a test that checks if the child fails to bail out of the loop
to prevent an infinite loop.

What this patch does is to still try any siblings in that directory.
If all the siblings fail, or there are no more siblings, then we exit
the loop.

This fixes the above symptom, but...

This is no full proof. It makes the debugfs_remove_recursive a bit more
robust, but it does not explain why the one file failed. There may
be some kind of delay deletion that makes the debugfs think it did
not succeed. So this patch is more of a fix for the symptom but not
the disease.

This patch still makes the debugfs_remove_recursive more robust and
until I can find out why the bug exists, this patch will keep
the kernel from oopsing in most cases. Even after the cause is found
I think this change can stand on its own and should be kept.

[ Impact: prevent kernel oops on module unload and reading debugfs files ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: function to know if debugfs is initialized

Impact: add new debugfs API

With ftrace, some tracers are registered in early initcalls
and attempt to create files on the debugfs filesystem.
Depending on when they are activated, they can try to create their
file at any time. Some checks can be done on the tracing area
but providing a helper to know if debugfs is registered make it
really more easy.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237759847-21025-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

zero i_uid/i_gid on inode allocation

... and don't bother in callers. Don't bother with zeroing i_blocks,
while we are at it - it's already been zeroed.

i_mode is not worth the effort; it has no common default value.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

integrity: special fs magic

Discussion on the mailing list questioned the use of these
magic values in userspace, concluding these values are already
exported to userspace via statfs and their correct/incorrect
usage is left up to the userspace application.

- Move special fs magic number definitions to magic.h
- Add magic.h include

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>

debugfs: Implement debugfs_remove_recursive()

debugfs_remove_recursive() will remove a dentry and all its children.
Drivers can use this to zap their whole debugfs tree so that they don't
need to keep track of every single debugfs dentry they created.

It may fail to remove the whole tree in certain cases:

sh-3.2# rmmod atmel-mci < /sys/kernel/debug/mmc0/ios/clock
mmc0: card b368 removed
atmel_mci atmel_mci.0: Lost dma0chan1, falling back to PIO
sh-3.2# ls /sys/kernel/debug/mmc0/
ios

But I'm not sure if that case can be handled in any sane manner.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: Pierre Ossman <drzeus-list@drzeus.cx>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: fix sparse warnings

extern does not belong in C files, move declaration to linux/debugfs.h
fs/debugfs/file.c:42:30: warning: symbol 'debugfs_file_operations' was not declared. Should it be static?
fs/debugfs/file.c:54:31: warning: symbol 'debugfs_link_operations' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Kobject: convert fs/* from kobject_unregister() to kobject_put()

There is no need for kobject_unregister() anymore, thanks to Kay's
kobject cleanup changes, so replace all instances of it with
kobject_put().


Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kobject: convert kernel_kset to be a kobject

kernel_kset does not need to be a kset, but a much simpler kobject now
that we have kobj_attributes.

We also rename kernel_kset to kernel_kobj to catch all users of this
symbol with a build error instead of an easy-to-ignore build warning.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kset: convert kernel_subsys to use kset_create

Dynamically create the kset instead of declaring it statically. We also
rename kernel_subsys to kernel_kset to catch all users of this symbol
with a build error instead of an easy-to-ignore build warning.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kobject: convert debugfs to use kobject_create

We don't need a kset here, a simple kobject will do just fine, so
dynamically create the kobject and use it.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kobject: remove struct kobj_type from struct kset

We don't need a "default" ktype for a kset. We should set this
explicitly every time for each kset. This change is needed so that we
can make ksets dynamic, and cleans up one of the odd, undocumented
assumption that the kset/kobject/ktype model has.

This patch is based on a lot of help from Kay Sievers.

Nasty bug in the block code was found by Dave Young
<hidave.darkstar@gmail.com>

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

[PATCH] pass dentry to audit_inode()/audit_inode_child()

makes caller simpler *and* allows to scan ancestors

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

debugfs: remove rmdir() non-empty complaint

Hi,

This patch kills the pointless debugfs rmdir() printk() when called on a
non-empty directory. blktrace will sometimes have to call it a few times
when forcefully ending a trace, which polutes the log with pointless
warnings.

Rationale:

- It's more code to work-around this "problem" in the debugfs users, and
you would have to add code to check for empty directories to do so (or
assume that debugfs is using simple_ helpers, but that would be a
layering violation).

- Other rmdir() implementations don't complain about something this
silly.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: add rename for debugfs files

Implement debugfs_rename() to allow renaming files/directories in debugfs.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

remove "struct subsystem" as it is no longer needed

We need to work on cleaning up the relationship between kobjects, ksets and
ktypes. The removal of 'struct subsystem' is the first step of this,
especially as it is not really needed at all.

Thanks to Kay for fixing the bugs in this patch.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: Remove misleading comments.

Just mention which error will be returned if debugfs is disabled. Callers
should be able to figure out themselves what they need to check.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: implement symbolic links

debugfs: implement symbolic links

Implement a new function debugfs_create_symlink() which can be used
to create symbolic links in debugfs. This function can be useful
for people moving functionality from /proc to debugfs (e.g. the
gcov-kernel patch).

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

DebugFS : file/directory removal fix

Fix file and directory removal in debugfs. Add inotify support for file removal.

The following scenario :
create dir a
create dir a/b

cd a/b (some process goes in cwd a/b)

rmdir a/b
rmdir a

fails due to the fact that "a" appears to be non empty. It is because
the "b" dentry is not deleted from "a" and still in use. The same
problem happens if "b" is a file. d_delete is nice enough to know when
it needs to unhash and free the dentry if nothing else is using it or,
if someone is using it, to remove it from the hash queues and wait for
it to be deleted when it has no users.

The nice side-effect of this fix is that it calls the file removal
notification.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

DebugFS : more file/directory creation error handling

Correct dentry count to handle creation errors.

This patch puts a dput at the file creation instead of the file removal :
lookup_one_len already returns a dentry with reference count of 1. Then,
the dget() in simple_mknod increments it when the dentry is associated
with a file. In a scenario where simple_create or simple_mkdir returns
an error, this would lead to an unwanted increment of the reference
counter, therefore making file removal impossible.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

DebugFS : file/directory creation error handling

Fix error handling of file and directory creation in DebugFS.

The error path should release the file system because no _remove will be called
for this erroneous creation.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

DebugFS : coding style fixes

Minor coding style fixes along the way : 80 cols and a white space.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

DebugFS : inotify create/mkdir support

Add inotify create and mkdir events to DebugFS.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

[PATCH] debugfs: add header file

debugfs needs include/linux/kobject.h for <kernel_subsys>.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

debugfs: check return value correctly

The return value is stored in "*dentry", not in "dentry".

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

debugfs: spelling fix

Change debufs_create_file() to debugfs_create_file().

Signed-off-by: Komal Shah <komal_shah802003@yahoo.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

[PATCH] r/o bind mount prepwork: inc_nlink() helper

This is mostly included for parity with dec_nlink(), where we will have some
more hooks. This one should stay pretty darn straightforward for now.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] inode-diet: Eliminate i_blksize from the inode structure

This eliminates the i_blksize field from struct inode. Filesystems that want
to provide a per-inode st_blksize can do so by providing their own getattr
routine instead of using the generic_fillattr() function.

Note that some filesystems were providing pretty much random (and incorrect)
values for i_blksize.

[bunk@stusta.de: cleanup]
[akpm@osdl.org: generic_fillattr() fix]
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] inode_diet: Replace inode.u.generic_ip with inode.i_private

The following patches reduce the size of the VFS inode structure by 28 bytes
on a UP x86. (It would be more on an x86_64 system). This is a 10% reduction
in the inode size on a UP kernel that is configured in a production mode
(i.e., with no spinlock or other debugging functions enabled; if you want to
save memory taken up by in-core inodes, the first thing you should do is
disable the debugging options; they are responsible for a huge amount of bloat
in the VFS inode structure).

This patch:

The filesystem or device-specific pointer in the inode is inside a union,
which is pretty pointless given that all 30+ users of this field have been
using the void pointer. Get rid of the union and rename it to i_private, with
a comment to explain who is allowed to use the void pointer. This is just a
cleanup, but it allows us to reuse the union 'u' for something something where
the union will actually be used.

[judith@osdl.org: powerpc build fix]
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Judith Lebzelter <judith@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Debugfs: kernel-doc fixes for debugfs

Fix kernel-doc and typos/spellos in fs/debugfs/.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Remove obsolete #include <linux/config.h>

Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

[PATCH] VFS: Permit filesystem to override root dentry on mount

Extend the get_sb() filesystem operation to take an extra argument that
permits the VFS to pass in the target vfsmount that defines the mountpoint.

The filesystem is then required to manually set the superblock and root dentry
pointers. For most filesystems, this should be done with simple_set_mnt()
which will set the superblock pointer and then set the root dentry to the
superblock's s_root (as per the old default behaviour).

The get_sb() op now returns an integer as there's now no need to return the
superblock pointer.

This patch permits a superblock to be implicitly shared amongst several mount
points, such as can be done with NFS to avoid potential inode aliasing. In
such a case, simple_set_mnt() would not be called, and instead the mnt_root
and mnt_sb would be set directly.

The patch also makes the following changes:

(*) the get_sb_*() convenience functions in the core kernel now take a vfsmount
pointer argument and return an integer, so most filesystems have to change
very little.

(*) If one of the convenience function is not used, then get_sb() should
normally call simple_set_mnt() to instantiate the vfsmount. This will
always return 0, and so can be tail-called from get_sb().

(*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the
dcache upon superblock destruction rather than shrink_dcache_anon().

This is required because the superblock may now have multiple trees that
aren't actually bound to s_root, but that still need to be cleaned up. The
currently called functions assume that the whole tree is rooted at s_root,
and that anonymous dentries are not the roots of trees which results in
dentries being left unculled.

However, with the way NFS superblock sharing are currently set to be
implemented, these assumptions are violated: the root of the filesystem is
simply a dummy dentry and inode (the real inode for '/' may well be
inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries
with child trees.

[*] Anonymous until discovered from another tree.

(*) The documentation has been adjusted, including the additional bit of
changing ext2_* into foo_* in the documentation.

[akpm@osdl.org: convert ipath_fs, do other stuff]
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nathan Scott <nathans@sgi.com>
Cc: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

VFS: Unexport do_kern_mount() and clean up simple_pin_fs()

Replace all module uses with the new vfs_kern_mount() interface, and fix up
simple_pin_fs().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

[PATCH] debugfs inode leak

Looking at the reiser4 crash, I found a leak in debugfs. In
debugfs_mknod(), we create the inode before checking if the dentry
already has one attached. We don't free it if that is the case.

These bugs happen quite often, I'm starting to think we should disallow
such coding in CodingStyle.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] mark f_ops const in the inode

Mark the f_ops members of inodes as const, as well as fix the
ripple-through this causes by places that copy this f_ops and then "do
stuff" with it.

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] mutex subsystem, semaphore to mutex: VFS, ->i_sem

This patch converts the inode semaphore to a mutex. I have tested it on
XFS and compiled as much as one can consider on an ia64. Anyway your
luck with it might be different.

Modified-by: Ingo Molnar <mingo@elte.hu>

(finished the conversion)

Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

[PATCH] remove duplicate get_dentry functions in various places

Various filesystem drivers have grown a get_dentry() function that's a
duplicate of lookup_one_len, except that it doesn't take a maximum length
argument and doesn't check for \0 or / in the passed in filename.

Switch all these places to use lookup_one_len.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Greg KH <greg@kroah.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!